PRETERITE OR IMPERFECT ?

How do I know when to use the Preterite Tense or the Imperfect Tense ?  This is a question that is often asked by students.  The question that should be asked is does the action occur once or more than once ?

The Preterite Tense or the simple past tense is used for actions which have taken place in the past but that have only occurred once.  Very often there is a time stated when the action took place such as last night (anoche), yesterday (ayer) or this morning (esta mañana). 

The Imperfect Tense is used to describe an action which has happened more than once in the past or something you used to do.

PRETERITE

Fui  a la playa ayer.  I went to the beach yesterday.

Ayer tuvé un helado.  Yesterday I had an ice cream.

Hablé con mi madre ayer.  I spoke with my mum yesterday.

IMPERFECT TENSE

Iba a la playa cada semana.  I used to go to the beach every week.

Tenía un perro.  I used to have a dog.

Hablaba francés en el colegio.  I spoke (used to speak) French at school.

WORDS WHICH WILL DECIDE IF PRETERITE OR IMPERFECT